This manual describes version 7.1.31 of SWI-Prolog. SWI-Prolog is
widely considered to be a robust and scalable implementation of the
Prolog language. It is widely used in education and research. In
addition, it is in use for 24 × 7 mission critical
commercial server processes. The site http://www.swi-prolog.org
is hosted using the SWI-Prolog HTTP server infrastructure. It receives
approximately 2.3 million hits and serves approximately 300 Gbytes on
manual data and downloads each month. SWI-Prolog applications range from
student assignments to commercial applications that count more than one
million lines of Prolog code.

SWI-Prolog has two development tracks. Stable releases have
an even minor version number (e.g., 6.2.1) and are released as
a branch from the development version when the development version is
considered stable and there is sufficient new functionality to justify a
stable release. Stable releases often get a few patch updates to deal
with installation issues or major flaws. A new
Development version is typically released every couple of weeks
as a snapshot of the public git repository. `Extra editions' of the
development version may be released after problems that severely
hindered the user in their progress have been fixed.

Known bugs that are not likely to be fixed soon are described as
footnotes in this manual.

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